<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>响应式网页代码</title>
    <link rel="stylesheet" href="./css/index.css">    
    <meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">   
<style>
    *{
        margin: 0;
        padding: 0;
/*        列表样式*/
        list-style: none;
/*        取消字体修饰样式*/
        text-decoration: none;
    }
    .container{
        width: 1200px;
        margin: auto;
    }
    @media (max-width:600px){
        .container{
            width: 100%;
/*            background: red;*/
        }
         .col{
            width: 100%;
            background: yellow;
        }
    }
    @media (min-width:800px){
        .container{
            width: 100%;
/*            background: red;*/
        }
         .col{
            width: 100%;
            background: yellow;
             margin-top: 10px;
        }
    }
    .container .col{
        width: 33.333333%;
        float: left;
        height: 100px;
        background: aqua;
    }
    .container::after{
        content: "";
/*        布局*/
        display: table;
/*        清楚全部样式浮动*/
        clear:both;
    }
    </style>
</head>
<body>
    <div class="container"></div>
    <div class="col">网页的左侧</div>
    <div class="col">网页的中间</div>
    <div class="col">网页的右侧</div>
</body>
</html>